A. Field of the Invention
The invention relates to an energy savings device or method that can be applied to a resistive, an inductive, or a capacitive load regardless of the respective impedance or inductance or capacitance of the load. More particularly, the invention relates to a linear control dimming device that is mounted in series with a resistive, an inductive or a capacitive load and that has access for power and operation to one side of an electrical line supplied to the load. A fluorescent light fixture or a motor for a fan or other device, for example, can be controlled by way of the linear control device or method according to the invention.
B. Description of the Related Art
The ability to control illumination levels is strongly desired, especially due to the rising energy costs. Such ability to control illumination levels is very important for establishments that require a great deal of lighting, such as restaurants and offices.
Lighting levels that are higher than necessary not only result in a higher energy costs associated with the lighting, but also can increase air conditioning costs due to the excess heat provided by the lighting fixtures. Fluorescent light fixtures output less heat than incandescent light fixtures for equivalent illumination, and thus they are becoming more popular with offices or other commercial establishments.
There currently exist various types of dimmer devices that can be used in order to control the amount of light output by fluorescent lights. One type utilizes a complex electronic ballast which first converts the applied AC line voltage to DC, then switches the applied tube voltage at high frequency. The resulting power-to-light output efficiency is hampered by this additional manipulation. This type requires an expensive fixture replacement and rewiring to the wall switch. Simplistic phase control devices will not provide satisfactory results when controlling a magnetic ballast fluorescent fixture.
FIG. 1A shows the connections of a conventional fluorescent dimmer device or controller 100, which is provided between a line and a load. The load is shown as a light fixture 110, which may be a fluorescent tube and associated ballast, for example. As shown in FIG. 1A, the conventional controller 100 needs access to both sides (line 102 and neutral 104) of an AC power input, in addition to the load. Since connectivity to the neutral line 104 is not always available at a light switch box, conventional fluorescent controllers may require expensive re-wiring to be installed.
The problem with using such a conventional dimmer circuit for a fluorescent lighting fixture is that the conventional dimmer circuit cannot modulate reactive loads. Reactive loads react with the controller, thereby producing oscillations that then cause surges of voltage and current, which are both unpredictable and uncontrollable. With such control being applied to a fluorescent light fixture, the typical result is a non-harmonic type of flickering, which frequently takes the light from zero output to maximum output and to values in between. Such flickering is visually (and also audibly) discomforting, and may even be unhealthful to people who are near the flickering fluorescent light (for example, it may cause headaches due to having to view the undesirable light flickering).
As explained earlier, a controller such as the one shown in FIG. 1A can be used to control a fluorescent light without causing significant flickering, but such a controller requires fairly substantial installation costs, since they cannot be installed at a light switch box (where a neutral line is not typically provided), but rather have to be installed very close to the ballast (e.g., in the ceiling of a room, where a neutral line is provided).
U.S. Pat. No. 5,043,635 to Talbott et al. describes a two-line power control device for dimming fluorescent lights, which does not require to be coupled to a neutral line. Accordingly, the Talbott et al. device can in theory be installed at a light switch box. However, due to the analog structure and the various components described in the Talbott et al. device, such a device is very difficult to manufacture, and also such a device is very difficult to manufacture in a small size. Thus, it is not feasible to install such a device in a light switch box, given the bulkiness as well as the transformer configuration of the Talbott et al. device.